The present invention relates to a method for heating a charge using a flame having a variable orientation with regard to the charge, this orientable flame being generated in particular by a lance and/or a burner and more particularly a lance and/or a burner comprising at least one channel for injecting at least one main jet, such as a jet containing oxidizer, fuel, or a premixture of oxidizer and fuel.
In practice, when the burner is designed, the conditions of interaction of the various jets or flows of oxidizer and fuel used by the burner are determined. Once the burner has been built, only the operating conditions can be modified.
The operating conditions of industrial combustion processes may evolve over time. This is inherently the case of intermittent processes, but it is also the case of continuous processes for which the characteristics of the charges to be heated may vary according to production requirements. It is more generally the case of any production unit subject to aging or sensitive to the variable conditions of its environment.
To adapt the performance of burners to variable operating conditions, the operator usually can only vary two parameters: the operating power of the burner and the excess oxidizer (oxygen superstoichiometry).
Some combustion technologies allow for discrete operating modes. This is the case for example of burners called “dual pulse” burners which use two different injection systems according to whether the burner is operated at low or high pulse. These two operating modes serve to increase the range of operation or use of the burner.
However, modifications of the operating point and/or mode are usually insufficient to optimize the performance of the burners or the processes using these burners under all conditions. For example, the cyclic introduction of solid material at ambient temperature into a melting furnace will lead the operator (or the control system) to increase the heating power so as to obtain the fastest possible fusion (in order to increase productivity), but without necessarily degrading the melting charge (product quality) nor overheating the furnace (equipment service life). This compromise between productivity and quality and/or service life depends in particular on the capacity of the system to transfer the energy to the charge, while avoiding local overheating of the charge or of the furnace refractories. This compromise is reflected by a melting time below which any gain in productivity is counterbalanced by a degradation of product quality or by the reduction of the furnace service life.
WO-A-9744618 teaches a burner comprising a central jet of fuel first surrounded by a plurality of jets of primary oxidizer, followed by a plurality of jets of secondary oxidizer. This makes it possible to modify the position of the flame during operation.
The use of variable direction flames in a furnace is also known from EPA-A-1213364.
It is the object of the invention to propose to control the heating of a charge without causing local overheating.